I was wondering if the robotic arms could draw or write with some level of accuracy. I was particularly interested in the accuracy of the erector set arm because of its customizability.
Also, I was wondering how quickly accurate moves could be made.
Thanks
Good question, but I can’t answer it. 
However, I’d suggest doing what I’m doing and just get the parts and prototype. It’s not that costly and I don’t know that anyone can answer the question well enough to satisfy your requirements. My “good enough” may not be good enough for you.
But perhaps I can answer this question in a few weeks after I get everything running. I would expect the arm will be as accurate as the servos * the length of the pieces your connecting, which would amplify any inaccuracies but unless you want to use encoders and keep track of all the yourself, it may be a best solution.
If you need a computer controlled drawing machine a plotter is the thing to buy/build.
Yeah, I guess it depends on what you’re using it for? A plotter is better if you want razor straight lines but if you want a funner “human-like” drawing hand then the arm would be interesting.
What exactly are you wanting to accomplish?
Well, the more hardware you use, the less accurate it’ll be.
Once you get everything bolted together and know that you’re going to keep it that way forever, Loctite or Super Glue is your best friend for reducing the mechanical flexing.
You can use the servo programmer to reduce the deadband of the servos, but you’ll never eliminate it.
It’s possible to get a very accurate hand by using some sort of feedback.
Video would probably be the most accurate (and the most complicated), but that’s just one option.
Without feedback, minor imperfections will build up.
